1. Field of the Invention
The present invention relates to a wireless terminal device of a system that simultaneously performs transmission and reception such as the CDMA (Code Division Multiple Access) system.
2. Description of the Background Art
In the terminal of a cellular phone employing the system that simultaneously performs transmission and reception such as the CDMA system, one antenna is often shared for transmission and reception. In this case, a transmission/reception branching filter is provided so as to convey a transmission wave from a transmitting circuit to the transmitting/receiving share antenna and to convey a reception wave from the transmitting/receiving share antenna to a receiving circuit, and also prevent the transmission wave from being conveyed to the receiving circuit. Furthermore, transmission and the reception may simultaneously be performed through an external connector, as in the case of a vehicle antenna to which the external connector is connected for use. In this case, the transmission/reception branching filter and an input/output port provided at the external connector are connected by a switch provided between the transmitting/receiving share antenna and the transmission/reception branching filter, so that the transmission wave is conveyed from the transmitting circuit to the vehicle antenna and the reception wave is passed from the vehicle antenna to the receiving circuit via the input/output port. Thus, transmission and reception are simultaneously performed via a single input/output port.
A wireless terminal device according to the invention corresponds to a system in which transmission and reception are simultaneously performed, and includes a transmitting circuit, a transmitting antenna, a receiving antenna, a receiving circuit, a single external input/output node and a transferring circuit. The transmitting circuit generates a transmission wave. The transmitting antenna emits the transmission wave outwards. The receiving circuit receives a reception wave from the receiving antenna. The transferring circuit transfers the transmission wave from the transmitting circuit to the external input/output node and transfers the reception wave from the external input/output node to the receiving circuit.
In the wireless terminal device, provision of the transferring circuit eliminates the necessity of providing the external input/output node corresponding to the transmitting and receiving circuits respectively. Transmission and reception can thus be simultaneously performed via the single external input/output node. Therefore, the wireless terminal device of the invention is compatible with a general wireless terminal device that simultaneously performs transmission and the reception by one transmitting/receiving shared antenna.
Preferably, the wireless terminal device of the invention further includes a first switching circuit and a second switching circuit. The first switching circuit is provided between the transmitting circuit and the transmitting antenna to selectively connect the transmitting circuit to the transmitting antenna or the transferring circuit. The second switching circuit is provided between the receiving circuit and the receiving antenna to selectively connect the receiving circuit to the receiving antenna or the transferring circuit.
According to the wireless terminal device, the transmission/reception by the transmitting/receiving antennas and the transmission/reception via the external input/output node can be switched selectively.
Preferably, the transferring circuit is a transmission/reception branching filter connected to the external input/output node, the transmitting circuit and the receiving circuit.
The transferring circuit preferably includes a first band pass filter and a second band pass filter. The first band pass filter is provided between the external input/output node and the first switching circuit to allow the transmission wave to pass therethrough and to block the reception wave. The second band pass filter is provided between the external input/output node and the second switching circuit to allow the reception wave to pass therethrough and to block the transmission wave.
According to the wireless terminal device of the invention, it is possible to suppress the transmission wave transferred from the transmitting circuit to the receiving circuit and the reception wave transferred from the external input/output node to the transmitting circuit.
The transferring circuit preferably includes a circulator. The circulator has a first terminal connected to the external input/output node, a second terminal connected to the second switching circuit, and a third terminal connected to the first switching circuit.
The circulator allows waves to pass therethrough in the direction from the first to the second terminals, from the second to the third terminals, and from the third to the first terminals, while blocking waves of the opposite direction therefrom. In other words, the circulator transfers the transmission wave from the transmitting circuit to the external input/output node and the reception wave from the external input/output node to the receiving circuit, while suppressing the transmission wave transferred from the transmitting circuit to the receiving circuit and the reception wave transferred from the external input/output node to the transmitting circuit.
Preferably, the wireless terminal device further includes a band pass filter provided between the second switching circuit and the receiving circuit to allow the reception wave to pass therethrough and block the transmission wave.
Preferably, the wireless terminal device further includes a band pass filter provided between the first switching circuit and the transmitting circuit to allow the transmission wave to pass therethrough and block the reception wave.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.